This invention relates to roll-up and other types of vertical industrial doors, and particularly to a door operator for opening and closing such doors both automatically and with manual override.
Industrial doors fall in two main categories: vertically opening and horizontally opening doors. Examples of the vertical doors are the roll-up type in which a sheet or series of slats are wound about a shaft at the top of the door opening, and the slat-type in which the door follows a vertical and then horizontal track. Examples of the horizontal doors are the slide-by type in which a door is suspended on a horizontal track and the accordion-type in which the articulated door panels are suspended from a horizontal track and are folded toward and away from the door opening.
Because industrial doors typically function to separate one environment from another, it is desirable that the doors be opened and closed rapidly, usually in response to automatic actuation. To that end, powered door operators have been developed which use either electric or hydraulic motors operating through a drive train and with suitable controls to move the door between its open and closed positions. An example of an hydraulic door operator is found in U.S. Pat. No. 4,296,570 issued Oct. 27, 1981 to Balbach, et al. and assigned to the assignee of this application.
Vertically opening doors present some requirements for control which are not present in horizontally opening doors because the weight of the door is suspended when it is partially or fully open and a loss of control could result in the door closing and causing injury to person or property. Furthermore, a vertical door cannot typically be easily manually opened in the case of a power failure or the like because of the weight of the door, whereas a horizontal door can usually be physically slid on the track.
The present invention provides an operator for an industrial door that will prevent rotation of the drive elements when there is a loss of power, but which permits manual override so that the door can be manipulated manually to open or close it.